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Abstract

The pecan weevil, Curculio caryae Horn, is an obligate nut feeder of all North American hickory
(Carya) and a key pest of the pecan, C. illinoinensis Koch. This study investigated population
structure of the pecan weevil. Gene flow and genetic variation was estimated for 90 pecan
weevil specimens sampled from the entire Carya range. Cladistic and nested clade analyses, as
well as an analysis of molecular variance (AMOVA) of mitochondrial DNA cytochrome oxidase
I (mtDNA COI) were performed. The data indicate C. caryae diverged from its sister species, C.
nasicus approximately 4.3 million years before present (mybp). Six-hundred and forty equally
parsimonious trees of 31 haplotypes demonstrated high genetic diversity across all pecan weevil
samples, and significant regional subdivision. Three clades recovered in the parsimony and
nested clade analyses were strongly associated with western, eastern and central localities
sampled within C. caryae's range. The current distribution of C. caryae and population structure
were explained by past glaciation events. Lineage divergence between the western and eastern
populations occurred during the Pleistocene (approx. 1.1 million years ago), and a more recent
divergence occurred between C. caryae populations east and west of the Appalachian mountain
range (870,000 yrs. ago). Haplotypes were segregated by region, but further sampling is
necessary to test for gene flow among these regions.